Pivot source files into top-level src,include and unify test target

See discussion in go/perfetto-build-files .
This is to disambiguate things like
  #include "base/logging.h"
when in the chrome tree.

Also this CL unifies the test targets into two monolithic targets:
perfetto_tests and perfetto_benchmarks. This is to avoid ending
up with confusing binary names in the chrome tree (e.g.,
ipc_unittests)

Bug: 68710794
Change-Id: I1768e15b661406052b2be060d7aab0f1e7443a98
diff --git a/gn/proto_library.gni b/gn/proto_library.gni
new file mode 100644
index 0000000..97b95d2
--- /dev/null
+++ b/gn/proto_library.gni
@@ -0,0 +1,23 @@
+# Copyright (C) 2017 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//build_overrides/build.gni")
+
+if (!build_with_chromium) {
+  # TODO(primiano): Just move //build/proto_library.gni inside this branch,
+  # there is no need to have that in //build at this point.
+  import("//build/proto_library.gni")
+} else {
+  import("//third_party/protobuf/proto_library.gni")
+}